1. Field of the Invention
The present invention relates to a PCV apparatus used for an engine of an automobile and the like. The PCV stands for Positive Crankcase Ventilation, and the PCV apparatus is a blowby gas returning apparatus.
2. Description of the Background Art
Generally, in an engine, mixture of fuel and air is combusted in a cylinder to generate energy, which is consumed by a piston for performing stroke motion. Some of the mixture does not burn and leaks into a crankcase through a gap of the piston. Such mixture of fuel and air leaking into the crankcase is referred to as blowby gases. The blowby gases include a large amount of incombustible gases such as carbon monoxide, hydrocarbon, and the like. The purpose of the PCV apparatus is to prevent the emission of such blowby gas into the atmosphere. FIG. 3 shows one example of an engine with the PCV apparatus. In the engine, a cylinder head 3 and cylinder block 4 are combined, with a head cover 2 covering over cylinder head 3. As shown in FIG. 3, in this engine the blowby gases are guided by a PCV piping 5 of the PCV apparatus which extends from the crankcase via head cover 2 to an intake manifold 10 which constitutes a part of an intake system.
The blowby gases contain a small amount of moisture. As such, the aforementioned engine with PCV piping 5 has been suffering from the malfunction of the PCV apparatus when used in cold climates, due to the moisture being frozen in the PCV piping.
Therefore, in order to prevent the moisture in the PCV piping from freezing, as shown in FIG. 4, it has been proposed to implement the PCV piping by a hose 21 passing blowby gases and a thermal insulating protector 22 wrapping the same. Further, as shown in FIG. 5, an arrangement is proposed in Japanese Utility Model Laying-Open No. 4-93710 in which hose 21 is provided with an external coaxial water path tube 23, to cause warm water to flow through the resulting space therebetween. Another proposed arrangement is shown in FIG. 6, in which hose 21 and water path tube 24 are positioned next to each other and brazed together, to cause warm water to flow through water path tube 24.
With any one of the arrangements of FIGS. 4 to 6, however, PCV piping 5 occupies much space and further complicates the arrangement, thus increasing the costs undesirably. In order to attain compactness, it has also been once contemplated to scale the overall structure down, which involved reduction of the diameter of the hose passing the blowby gasses. In such a case, undesirable clogging tends to occur in the hose, and thus the risk of freezing increases against the original intention.
The object of the present invention is to provide a PCV apparatus which prevents piping from freezing with a compact arrangement, which can be implemented at low cost.
In order to achieve the aforementioned object, the PCV apparatus according to the present invention returns, in an engine having crankcase and an intake system, blowby gases leaked into the crankcase back to the intake system. The PCV apparatus includes a PCV piping forming at least part of a path through which the blowby gases return, and a heat transmitting member connecting a prescribed portion of the engine and the PCV piping, enabling heat transmission. By employing this arrangement, heat of the engine is transmitted to the PCV piping via the heat transmitting member, and thus the moisture in the PCV piping is prevented from freezing.
Preferably in the aforementioned invention, the prescribed portion of the engine is a heat emitting region which emits heat resulted from a combustion or frictional motion therein. By employing this arrangement, the heat from the heat emitting region can continuously be transmitted to the PCV piping, ensuring that the moisture of the PCV piping will not be frozen.
Preferably in the aforementioned invention, the PCV piping is mainly made with metal. By employing this arrangement, since the PCV piping is mainly made with metal and thus has high thermal conductivity, it can receive heat from the heat transmitting member quickly, ensuring that the moisture of the PCV piping will not be frozen.
Preferably in the aforementioned invention, the heat transmitting member is made of a material having higher thermal conductivity than the PCV piping. By employing this arrangement, the heat transmitting member will distribute heat widely in itself quickly, before transmitting heat from the engine to the PCV piping, thus passing heat to wide range of the PCV piping.
Preferably in the aforementioned invention, the PCV piping is arranged outside to the engine at a portion where the PCV piping is not subjected to the air flow generated by driving an automobile with the engine. By employing this arrangement, the PCV piping will not be cooled, since it will not be subjected to the air flow generated by driving an automobile directly, and thus the moisture in the PCV piping is prevented from freezing.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.